What is the recommended treatment for a pregnant woman diagnosed with a Group B strep (Streptococcus agalactiae) urinary tract infection (UTI)?

Treatment of Group B Streptococcus UTI in Pregnancy

For pregnant women with Group B Streptococcus (GBS) urinary tract infection, treatment with penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours) is recommended, followed by intrapartum antibiotic prophylaxis during labor regardless of previous treatment. 1

First-line Treatment Options

For the treatment of GBS UTI in pregnancy, the CDC recommends:

• First-line options:
  • Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours
  • Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours 1

These antibiotics remain highly effective as GBS continues to be universally susceptible to penicillin and ampicillin 1, 2. Recent research from 2024 confirms that all GBS strains tested were fully sensitive to penicillin and ampicillin 2.

Alternative Treatment Options (Penicillin Allergy)

For patients with penicillin allergy, the CDC recommends:

• Alternative options:
  • Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours
  • Clindamycin: 900 mg IV every 8 hours
  • Vancomycin: 1 g IV every 12 hours 1

Important: Susceptibility testing is essential when using alternatives to penicillin, especially for clindamycin, due to increasing resistance 1, 3. Recent data shows high resistance rates for clindamycin (77.34%) 2.

Duration of Treatment

• Treat for 5-7 days for uncomplicated UTIs
• Treat for 10-14 days for complicated UTIs or pyelonephritis
• Continue treatment for at least 48-72 hours after symptoms resolve 1

Key Clinical Considerations

1. Any colony count is significant: GBS in urine at any colony count indicates heavy genital tract colonization and should be treated 1

2. Both symptomatic and asymptomatic infections require treatment: All pregnant women with GBS bacteriuria should receive appropriate antibiotic treatment 1

3. Intrapartum prophylaxis is mandatory: All women with GBS bacteriuria during pregnancy require intrapartum antibiotic prophylaxis during labor, regardless of whether they received treatment earlier in pregnancy 1

4. Recolonization is common: Antibiotics do not eliminate GBS from genitourinary and gastrointestinal tracts, and recolonization after treatment is typical 1

5. Optimal dosing interval: Research indicates that the dosing interval for penicillin G should be 4 hours to ensure anti-GBS activity in all patients 4

Intrapartum Antibiotic Prophylaxis

During labor, the same first-line antibiotics are recommended:

• Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery 1

This prophylaxis significantly reduces vertical transmission of GBS to the newborn. Early research demonstrated that none of the infants whose mothers received ampicillin during labor were colonized with GBS, compared to 58% of infants whose mothers received no antibiotics 5.

Common Pitfalls to Avoid

1. Failing to treat asymptomatic bacteriuria: Any colony count of GBS in urine during pregnancy requires treatment 1

2. Omitting intrapartum prophylaxis: Even if GBS UTI was treated earlier in pregnancy, intrapartum prophylaxis is still required 1

3. Using clindamycin without susceptibility testing: Due to high resistance rates, clindamycin should only be used after confirming susceptibility 1, 2

4. Attempting to eradicate colonization: Treating GBS colonization with oral antibiotics in the third trimester is ineffective, as 30-70% of treated women remain colonized at delivery 1